/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import com.sun.org.apache.bcel.internal.Constants;
import com.sun.org.apache.bcel.internal.classfile.Utility;
import com.sun.org.apache.bcel.internal.classfile.ConstantPool;
import java.io.*;
import com.sun.org.apache.bcel.internal.util.ByteSequence;

/**
 * Abstract super class for all Java byte codes.
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 */
public abstract class Instruction implements Cloneable, Serializable {
    protected short length = 1; // Length of instruction in bytes
    protected short opcode = -1; // Opcode number

    private static InstructionComparator cmp = InstructionComparator.DEFAULT;

    /**
     * Empty constructor needed for the Class.newInstance() statement in
     * Instruction.readInstruction(). Not to be used otherwise.
     */
    Instruction() {
    }

    public Instruction(short opcode, short length) {
        this.length = length;
        this.opcode = opcode;
    }

    /**
     * Dump instruction as byte code to stream out.
     * @param out Output stream
     */
    public void dump(DataOutputStream out) throws IOException {
        out.writeByte(opcode); // Common for all instructions
    }

    /** @return name of instruction, i.e., opcode name
     */
    public String getName() {
        return Constants.OPCODE_NAMES[opcode];
    }

    /**
     * Long output format:
     *
     * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]"
     * "("&lt;length of instruction&gt;")"
     *
     * @param verbose long/short format switch
     * @return mnemonic for instruction
     */
    public String toString(boolean verbose) {
        if (verbose)
            return getName() + "[" + opcode + "](" + length + ")";
        else
            return getName();
    }

    /**
     * @return mnemonic for instruction in verbose format
     */
    public String toString() {
        return toString(true);
    }

    /**
     * @return mnemonic for instruction with sumbolic references resolved
     */
    public String toString(ConstantPool cp) {
        return toString(false);
    }

    /**
     * Use with caution, since `BranchInstruction's have a `target' reference which
     * is not copied correctly (only basic types are). This also applies for
     * `Select' instructions with their multiple branch targets.
     *
     * @see BranchInstruction
     * @return (shallow) copy of an instruction
     */
    public Instruction copy() {
        Instruction i = null;

        // "Constant" instruction, no need to duplicate
        if (InstructionConstants.INSTRUCTIONS[this.getOpcode()] != null)
            i = this;
        else {
            try {
                i = (Instruction) clone();
            } catch (CloneNotSupportedException e) {
                System.err.println(e);
            }
        }

        return i;
    }

    /**
     * Read needed data (e.g. index) from file.
     *
     * @param bytes byte sequence to read from
     * @param wide "wide" instruction flag
     */
    protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException {
    }

    /**
     * Read an instruction from (byte code) input stream and return the
     * appropiate object.
     *
     * @param file file to read from
     * @return instruction object being read
     */
    public static final Instruction readInstruction(ByteSequence bytes) throws IOException {
        boolean wide = false;
        short opcode = (short) bytes.readUnsignedByte();
        Instruction obj = null;

        if (opcode == Constants.WIDE) { // Read next opcode after wide byte
            wide = true;
            opcode = (short) bytes.readUnsignedByte();
        }

        if (InstructionConstants.INSTRUCTIONS[opcode] != null)
            return InstructionConstants.INSTRUCTIONS[opcode]; // Used predefined immutable object, if available

        /* Find appropiate class, instantiate an (empty) instruction object
         * and initialize it by hand.
         */
        Class clazz;

        try {
            clazz = Class.forName(className(opcode));
        } catch (ClassNotFoundException cnfe) {
            // If a class by that name does not exist, the opcode is illegal.
            // Note that IMPDEP1, IMPDEP2, BREAKPOINT are also illegal in a sense.
            throw new ClassGenException("Illegal opcode detected.");
        }

        try {
            obj = (Instruction) clazz.newInstance();

            if (wide && !((obj instanceof LocalVariableInstruction) || (obj instanceof IINC) || (obj instanceof RET)))
                throw new Exception("Illegal opcode after wide: " + opcode);

            obj.setOpcode(opcode);
            obj.initFromFile(bytes, wide); // Do further initializations, if any
            // Byte code offset set in InstructionList
        } catch (Exception e) {
            throw new ClassGenException(e.toString());
        }

        return obj;
    }

    private static final String className(short opcode) {
        String name = Constants.OPCODE_NAMES[opcode].toUpperCase();

        /* ICONST_0, etc. will be shortened to ICONST, etc., since ICONST_0 and the like
         * are not implemented (directly).
         */
        try {
            int len = name.length();
            char ch1 = name.charAt(len - 2), ch2 = name.charAt(len - 1);

            if ((ch1 == '_') && (ch2 >= '0') && (ch2 <= '5'))
                name = name.substring(0, len - 2);

            if (name.equals("ICONST_M1")) // Special case
                name = "ICONST";
        } catch (StringIndexOutOfBoundsException e) {
            System.err.println(e);
        }

        return "com.sun.org.apache.bcel.internal.generic." + name;
    }

    /**
     * This method also gives right results for instructions whose
     * effect on the stack depends on the constant pool entry they
     * reference.
     *  @return Number of words consumed from stack by this instruction,
     * or Constants.UNPREDICTABLE, if this can not be computed statically
     */
    public int consumeStack(ConstantPoolGen cpg) {
        return Constants.CONSUME_STACK[opcode];
    }

    /**
     * This method also gives right results for instructions whose
     * effect on the stack depends on the constant pool entry they
     * reference.
     * @return Number of words produced onto stack by this instruction,
     * or Constants.UNPREDICTABLE, if this can not be computed statically
     */
    public int produceStack(ConstantPoolGen cpg) {
        return Constants.PRODUCE_STACK[opcode];
    }

    /**
     * @return this instructions opcode
     */
    public short getOpcode() {
        return opcode;
    }

    /**
     * @return length (in bytes) of instruction
     */
    public int getLength() {
        return length;
    }

    /**
     * Needed in readInstruction.
     */
    private void setOpcode(short opcode) {
        this.opcode = opcode;
    }

    /** Some instructions may be reused, so don't do anything by default.
     */
    void dispose() {
    }

    /**
     * Call corresponding visitor method(s). The order is:
     * Call visitor methods of implemented interfaces first, then
     * call methods according to the class hierarchy in descending order,
     * i.e., the most specific visitXXX() call comes last.
     *
     * @param v Visitor object
     */
    public abstract void accept(Visitor v);

    /** Get Comparator object used in the equals() method to determine
     * equality of instructions.
     *
     * @return currently used comparator for equals()
     */
    public static InstructionComparator getComparator() {
        return cmp;
    }

    /** Set comparator to be used for equals().
     */
    public static void setComparator(InstructionComparator c) {
        cmp = c;
    }

    /** Check for equality, delegated to comparator
     * @return true if that is an Instruction and has the same opcode
     */
    public boolean equals(Object that) {
        return (that instanceof Instruction) ? cmp.equals(this, (Instruction) that) : false;
    }
}
